Of all the men whom I have mentioned above, Malpighi and Leeuwenhoek are probably the best known to our readers for the large number and important character of the contributions which they made to microscopic anatomy. The list of Malpighi’s achievements, for example, includes the following, in addition to the demonstration of the blood in actual circulation, as already mentioned: contributions to our knowledge of the finer structure of plants; the demonstration of the minute anatomy of the skin (“_rete mucosum_” or “_rete Malpighi_”); the amplification of our knowledge of the structure of the teeth; the discovery that the lungs are composed to a large extent of terminal vesicles, the walls of which are richly supplied with blood-channels.; the demonstration that certain glands possess an acinous structure (_i.e._, an outlet channel springing from numerous small sacs, the whole group resembling a cluster of grapes); more complete details regarding the structure of the spleen and the kidneys (“Malpighian bodies or corpuscles”); additions to our knowledge of the structure of the white and the gray substances of the brain and the demonstration that fibres from the spinal cord pass on into the brain; the declaration that the papillae of the tongue are organs of taste and the papillae of the skin are organs of the sense of touch; and not a few other contributions of greater or less importance. During his long life Anton Leeuwenhoek (1632–1723) of Delft, Holland, made a great many additions to microscopic anatomy, some of the more important of which are the following: he was the first to discover and to describe the many varieties of Infusoria (the animalcules found in stagnant collections of water); to him is also due the credit of first observing the faceted arrangement in the eyes of insects; he made original investigations into the origin and mode of development of several species of the lower organisms; he was the first to observe the canaliculated mode of construction in bone, and he also noted the existence of the so-called bone-corpuscles (afterward rediscovered and more accurately described by Purkinje); he discovered the striated condition of the bundles of muscular fibres, and was also the first person to teach the doctrine that the growth of muscles is effected by an enlargement of the primitive bundles of fibres and not by a multiplication of these structures; he taught further that muscle-substance consists of numberless small spheres; he was the first to describe the crystalline lens as a structure composed of fibres which are arranged in layers or sheets; in association with Guillaume Molyneux he studied, under the microscope, the speed with which the blood-current travels in the blood-vessels; he made valuable observations on the nature of the spermatozoa; and, finally, the very first studies in bacteriology appear to have been made by Leeuwenhoek. As a result of his discovery of “round, rod-shaped, thread-like and